1. Field of the Invention
The present invention relates to an improved apparatus for testing the tensile strength of sheet material and in particular fibrous sheet material, such as paper.
2. Description of the Prior Art
Reference is made to U.S. Pat. No. 3,707,119, issued Dec. 26, 1972, by Wavell F. Cowan. In that patent an apparatus is described which comprises pairs of opposed clamping jaws wherein each pair of jaws is adapted to engage between them a portion of the sheet material adjacent that portion gripped by the opposed pair of jaws. Means are provided for controlling the pressure of each pair of clamping jaws on the sheet material. A support member is also provided for pivotally mounting one of the opposed pairs of clamping jaws relative to the other for pivotal movement between a first position whereby the opposed pairs of clamping jaws are juxtaposed in contact with each other and a position spaced apart from each other with the clamping jaws still gripping portions of the sheet. Motive means are provided for causing the pivotal movement of one pair of jaws relative to the other, said means including a fluid-operated piston and cylinder arrangement connected between the opposed pairs of jaws whereby a fluid load in the cylinder causes the opposed pairs of jaws to move away from said first position when the fluid load has overcome the tensile strength of the sheet gripped by the opposed pairs of jaws. Means are also provided for recording the fluid load required to overcome the tensile strength of the sheet material whereby the tensile strength of the sheet material can be conventionally measured.
It has been found that although the apparatus described in the above-mentioned patent performs with excellent results, it has been found, for one thing, that it cannot be used in situations of automatic continuous feeding since there is no clear through path through the jaws.